Electromagnetic devices usually include electrically conductive windings, wound or assembled in close physical proximity to ferromagnetic materials. The ferromagnetic materials and windings in combination produce directed magnetic paths or circuits suited for particular applications. Applications such as electric motors, solenoids, relays, generators and some sensors contain movable components which are generally referred to as rotors, while the fixed, or non-movable components are known as stators. Stators usually include the non-movable windings and ferromagnetic materials in a configuration to meet the purpose of the device. The present invention is concerned with improvements in such stators.
A conventional prior art stator configuration might include a sequence of individually wound coils, or current loops wound or later positioned in an annular array. Such a series of rectangular loop coils 10 is illustrated in FIG. 1A. FIG. 1A is a diagrammatic representation of only a portion of the windings necessary for establishing the operative magnetic fields in such a conventional device. The coils are wound from a continuous conductive filament one complete coil at a time. The successive coils or current loops are subsequently arranged in an annular or ring configuration and are here shown schematically laid out in a flat array. Successive current loops with multiple turns of wire filament per loop are wound or assembled to afford opposite adjacent polarities so that the radially directed field axes are alternately oppositely directed in and out. Thus, with current flowing in the direction of arrow 11, current loops 12a and 12b establish fields directed out of the plane of the paper while current loops 14a and 14b establish magnetic fields directed into the plane of the paper according to the right hand induction rule. For multiphase stator applications additional identical coil sets would be assembled and appropriately spaced or offset from the first set.
A simplified equivalent circuit of the prior art stationary field windings of FIG. 1A is shown in FIG. 1B where the current is oriented successively in opposite directions around the successive rectangular current loops 12a, 14a, 12b, 14b. The field direction is again shown according to the convention where a dot represents the magnetic field directed out of the plane of the paper and the cross or "x" represents the field directed into the plane of the paper.
A major disadvantage of the conventional construction is that the coil sets must be carefully assembled after the winding step is completed. Thus, the individually wound coils if wound successively from a single wire filament must be oriented properly afterwards. If the coils are wound separately from separate wire filaments, tedious interconnection between the coils is then required with attention again directed to proper orientation. The final assembly must be a supported configuration, with individual coils having the proper relative position and orientation to each other. Winding alone does not result in such final relationship according to conventional methods. The additional handling and manipulation of the coils that is required is undesirable because of the risk of damage to the wire filament as well as the added cost.